Arbitrary waveform generation in frequency shifting loops

We have demonstrated another promising application of FSF lasers to microwave photonics. An injected FSF loop makes it possible to generate a frequency comb whose spectral phase is quadratic and adjustable. The output field of this laser is therefore equivalent to that of a locked mode laser, after propagation in a dispersive line inducing group velocity dispersion, that is to say a pulse exhibiting frequency drift. (or "chirp"). In the case of the FSF laser, the rate of "chirp" as its sign are very easily adjustable by slightly changing the parameters of the FSF cavity.

By recombining the "chirped" optical pulse with the injection laser (heterodyning), the optical frequencies are brought back to the RF domain to produce "chirped" RF signals. The great simplicity of the device and the remarkable properties of the technique (repeatability, consistency of chirp chirp, flexibility, etc ...) led us to file a patent, currently being extended. This work could have applications in radar (FMCW, pulse compression), in RF spectroscopy, or in characterization of RF components.